Good evening,

I have a skoda octavia 1.5 tsi dsg7 etec 2021

and from the first day at high speeds on the motorway from 100 km/h and above the car shows an instability and goes a little to the right and immediately after a little to the left

it does it also without strong wind and in sport mode with the steering stable 

the dealer said that there isn’t  something wrong with the car when he looked at it and said it could be the fact that the car has a very soft suspension Has anything similar happened to anyone?

?

What tyres are fitted / Brand?

What pressures do you have them at for the load carried?

 

Did the dealership take the car into the workshop for their Master Tech to inspect and check the transport blocks were removed at the PDI?

Tyres Michelin primacy 4 205/55/r17 91v

The pressure is right and I tried with a lower pressure too and transport blocks are removed 

I have 4 Michelin Primacy 4 sitting with just a few miles done from new that were taken off after a week of getting my New Corsa electric & hve sat for 3 years.

They were crap and i might as well dump them because i would not give them to my worst enemy.

On Friday new all season tyres are going on my new Mini Electric because the GoodYear F1 tyres it came with are actually even worse than those Primacy 4 were on the Corsa.   (205/45 R 17,s in both cases) 

ECO Tyres, not by price but by design to give more miles and use less fuel by having less friction / grip & ultimately safety for you, loved ones and innocent people around you IMO.

Edited 22 August, 20232 yr by toot

24 minutes ago, Alexander1234 said:

from the first day at high speeds on the motorway from 100 km/h and above the car shows an instability and goes a little to the right and immediately after a little to the left

Maybe an issue with "lane enforce"? George, Ashley Neal has similar feelings about it to I do, and for much the same reasons.

Edited 22 August, 20232 yr by Paws4Thot

The answer is then disable it / switch off, to see if it is enabled and having an adverse affect like weaving the car where there are lane marking.

 

PS

First days with new tyres / cars they have 'Green Tyres' so as well as checking / resetting tyre pressures and the TPMS, 

you have to Run / Wear them in a bit and not just treat them like used tyres on a used car.

So many brand new cars / demonstrators, are in accidents before getting far from collection because of new tyres and drivers not engaging their brain.

Edited 22 August, 20232 yr by toot

The same thing is happening with the lane assist off 

What is the road surface like? Many cars will be slightly unstable if there are ruts in the asphalt. Some tire patterns will further pronounce it more than others.

On mine I have exactly this kind of "instability" on surfaces such as those mentioned by @Jorgeminator
If the road is "wave-like" for various reasons, the car starts behaving like a boat above certain speeds. If it's on a straight line I can live with it. But it sometimes occurs on some curvy-road and the combination of centrifugal force with the boat-on-top-of-waves behavior makes it really dangerous. I learnt to deal with it on roads that I know already, but I'm quite worried about it happening on roads that I don't know. And just to be clear: I'm not talking about driving at the limits of the car or the limit-speed for those curves. On those very same roads and asphalt-waves, my 15 y-old Megane drives great at the same speed.

I partially blame myself for the "bouncy" mk4, because I added the "rough-roads pack" on mine when I configured it. It could be an effect of comfy-suspension combined with increased ride-height...

I don't remembrer the drive-test car having a similar behavior, but on the other hand the test-trip was quite short and done on pretty good roads.

It’s happening when I drive on motorway from speeds at 100km/h and above and the road is good straight clean without bumps and it’s going a little to the right and then a little to the left with the steering straight and when it’s windy outside it’s a lot worse 

Ok, what you describe is clearly different from what I experience.
There's really no reason the car should wobble right-left on it's own on a straight-flat road without external factors, such as strong side-wind.
Are you sure it's also doing that with the Lane Assist turned off? If so, you should definitely go for a road-test with a Skoda mechanic onboard. See if they still tell you it's normal behavior...
Did you get the chance to have a test-drive with another similar car?

Yes I tried with the lane assist off a lot of times 

the lane assist turns the steering to move the car

my car is moving with the tires and steering straight like the wind is moving it 

the dealer said that he drove it and saw it and said that it’s due to the fact that the car has soft suspension so if the car goes with speed the wind from the speed hits the car and the suspension can’t keep the car straight because is soft 

I tried with the setting on sport suspension  and the same thing happens 

Other similar cars cheaper with worse specs that I’ve had  don’t do that 

But if other mk4s don’t do that thing it’s not that reason that the dealer said 

I’ll go to another dealer 

It's a nonsense what that dealer told you... If there's no (or weak) side-wind, the car will not (should not) go to the right or left simply because there is front wind resistance.
Just change the dealer if that was the answer of the current technician you're visiting.
If you mentioned sport suspension setting we can understand you have DCC on you Octavia? On Sport setting it should be clearly "stiffer" than standard (non-DCC) suspension. So once again, the dealer would have no reason to say "the car has soft suspension".

I suspect the tyres if the transport blocks are really removed.

But if they were still there it would not be soft suspension.

 

If the tyres are staying and the car is staying i would be taking it to a professional for a PROPER Alignment check.

Someone / someplace with all the gear, knows how to use it and with all the scores on the doors for your vehicle.